Magnification devices, such as telescopes used, for example, with rifles or other types of firearms are useful in increasing a user's accuracy with the firearm by increasing the size of and improving the focus of the image of objects of interest within the field of view of the telescope.
Due to the size of the diameter of the eyepiece lenses of many telescopes much reflected light is allowed to enter the user's eye and impinge on the user's retina. Because of this, the sharpness of the focus of objects within the field of view of the telescope is degraded. This occurs because light that is reflected onto the user's retina decreases the contrast of the objects of interest within the telescope field of view which causes the objects of interest to appear less sharp to the user. This results in a decrease in the user's accuracy with the firearm.
Other types of magnification devices, such as binoculars and camera lenses have large diameter viewing lenses located at the end where light enters the magnification devices. These viewing lenses also allow much reflected light into the eye and similarly decrease the contrast of objects within the field of view of the device.
Thus, while telescopes and other magnification devices alone provide increased sharpness of focus they do have certain limitations and drawbacks that do not provide the user with optimum imaging of objects of interest within the field of view of the devices.